CHEMICAL MICROSCOPY 



281 



result was employed by the Koflers to restrict determination of the 

 temperature-composition diagram to index measurements using the 

 glass-powder method. First, the glass powder is inserted between 

 the object-slide and the cover-slip, the contact method being prepared 



p^j^g Compositioo 



Fig, 11.18. Determination of eutectic point composition. 



Pyre Composition Pure 



Fig. 11.19. Determination of addition compound composition (M). 



as usual. Let us now determine the eutectic point. Next, the specimen 

 is heated on the hot stage and, as the glass particles are scattered 

 throughout the specimen, some of them are always present in the 

 eutectic area. One such particle is observed as the eutectic is mehing. 

 If the glass-particles index is adequate, a time comes, as temperature 

 rises, when the particle is no longer visible, i.e. its index is the same 

 as the hquid's, this corresponding to point M in Fig. 11.18. At the 

 temperature /g, the melted eutectic mixture has an index of 1-530. 



